Torque release means for rotary pneumatic tools



s. AKE BRATT 3, 7

TORQUE RELEASE MEANS FOR ROTARY PNEUMATIC TOOLS Get. 21, 1969 Filed Oct.10, 1967 0 IXYEXI L" Sven AKe Bmtt.

QWWKW United States Patent US. Cl. 91-59 7 Claims ABSTRACT OF TIEDISCLOSURE The invention provides a rotary pneumatic torque release toolhaving a vane motor in which a control mechv anism is triggered by thedevelopment of a predetermined torque in the motor cylinder and acts toeffect the operation of the tool. The tool comprises a housing and aWorking cylinder in said housing containing a vane motor rotatablymounted between inlet and outlet ports in said working cylinder. Themotor drives the tool. The housing contains an air supply connection forconnecting said inlet port to a source of compressed air. The housingalso contains a control mechanism which is effected by an adjustablepressure-sensing means operatively connected to said control mechanismwhich acts to release said control mechanism in response to apredetermined raise in the pressure sensed by said sensing means. Saidpressuresensing means is connected by a passage means in said housingseparate from said connection with an orifice in said cylinder andthereby subjected to the driving pressure acting directly on the vanesfor rotating said motor. An increase in said driving pressure is sensedby said pressure-sensing means which triggers said control mechanismwhen a predetermined rise is determined.

In a torque release means for rotary pneumatic tools including acompressed air driven vane motor and a normally open shut-off valve forclosing the air supply connection to the motor, a piston element on theshut-off valve is connected to an orifice in the working cylinder of thevane motor for sensing the drive pressure therein acting directly on thevanes thereby to shut off the valve against the pressure in the airconnection when a predetermined raise in pressure is reached in theworking cylinder.

This invention relates to torque release means for rotary pneumatictools. More particularly the invention is concerned with rotarypneumatic torque release tools such as nut setters, screw drivers andthe like, of the type incorporating a control mechanism therein whichupon the development of a predetermined drive torque in the tool isreleasable to perform a control movement affecting the operation of thetool. The operation of the tool is normally affected in a manner toenable control of the torque output of the tool in order to protect theWork against being overloaded or to run the work to the desired degreeof tightness. It has been suggested (US. Patent 2,923,306 to W. G.Mitchell) to base the operation of the control mechanism on sensing ofthe pressure in the air supply connection to the tool and to releasemovement of the control mechanism when a predetermined pressure raise isreached therein. However, if one compares the pressure in the air inletduring idle rotation of for example a nut setting tool and duringtransmission of nearly maximal torque thereby, there is normally noted apressure raise in the connection in the order of magnitude of half anatmosphere or less. It is therefore diificult during the rough operationto which nut setting tools are subjected ice in practice, to release thecontrol mechanism with sufficient quickness and accuracy in order toassure protection against overloading or to receive, during tighteningof series of nuts, sufiiciently small variations from case to case inthe final torque reached.

It is the main object of the invention to increase, in torque releasecontrol mechanism of the type in question, the magnitude of the pressuredifferential acting to release the mechanism and to adapt theconstruction thereof to this increased pressure differential so thatoverload protection and control of the final torque can be had withsubstantially increase dependability. For these and other purposes thereis according to the invention provided a rotary pneumatic torque releasetool comprising a housing, a working cylinder in said housing, a vanemotor rotatably mounted between inlet and outlet ports in said cylinderfor driving said tool, an air supply connection for connecting saidinlet port to a source of compressed air, a control mechanism in saidhousing to be released for performing a control movement aifecting theoperation of said tool upon the development of a predetermined torquetherein, adjustable pressure sensing means operatively connected to saidcontrol mechanism for releasing said control movement thereof inresponse to a predetermined raise in the pressure sensed by said sensingmeans, and passage means in said housing separate from said connection,said passage means communicating said sensing means with an orifice insaid working cylinder subjected to the drive pressure therein actingdirectly on the vanes for rotating said motor.

Because of fiow losses and expansion in the air motor the activepressure at the orifice of the disclosed torque release tool may fallbelow the incoming line pressure in the connection by severalatmospheres. At increased torque transmission the air flow through themotor is successively diminished. By reason thereof the fiow losses arealso reduced and expansion in the motor is counteracted due to leakagepast the motor vanes and thus the pressure raises and approaches theline pressure. The pressure differential which may be used for releasingthe control mechanism is thus doubled many times over whereby a moreaccurate release may be attained.

The above and other objects of the invention will become obvious fromthe following description and from the accompanying drawing in which apreferred embodiment of the invention is illustrated by way of example.It should be understood that this embodiment is only illustrative of theinvention and various modifications may be made within the scope of theclaims.

In the drawing FIG. 1 shows a longitudinal section through a rotarytorque release tool embodying the invention. The longitudinal section istaken along the line 11 in FIG. 2. FIG. 2 is a cross section on the line2-2 in FIG. 1.

In the figures there is shown a nut setting tool 10 provided with acompressed air driven vane motor 11. The motor 11 carries radial drivingvanes 12 which rotate in a working cylinder 13. The motor 11 is coupledvia planetory gearing 14 to an axle 15 which via angle gearing 16 drivesa square driving boss 17.

Compressed air is supplied via a hose, not shown, to the rear end of thenut setting tool from which an air supply connection 18 -18 extendsforwardly within the nut setting tool 10 to the air inlet 19, FIG. 2, inthe working cylinder 13 of the vane motor 11. In the air supplyconnection portion 18 is arranged a throttle valve 20 which is kept inclosed position by a spring 21 and may be opened manually by depressionof a trigger 22.

Upstream of the throttle valve 20 there is arranged between the airsupply connection portions 18 and 18 a valve seat 23 and a controlmechanism provided by a shut-off valve 24 cooperating with the seat foraffecting operation of the tool by a control movement shutting off theair supply. The shut-oil valve 24 consists of a piston element 26, 27which is slidably and sealingly guided in a valve housing 25. When theshut-off valve 24 is open, its forward piston face 26 is subjected tothe pressure in the air suppy connection 18 adjacent to the valve seat23. The opposed piston face 27 of the shut-off, valve 24 faces aninterior chamber in the valve housing 25 and is actuated by a helicalspring 28. The rear end of the latter is supported by a flange on ashell 29 which is sealingly slidable on a cylindrical part 31} in thevalve housing 25. A set screw 31 is threaded into the part 30 and bearsaagins the bottom of the shell 29. By axial adjustment of the set screw31 one thus can pre-load the spring 28 to the desired extent.

A passage 32 connects the chamber of the valve hous ing 25 with anorifice 33 in the working cylinder 13. The orifice 33 is preferablydisposed in the sector of the working cylinder 13 which is bounded bythe closing edge 34 of the air inlet 19 and half the angular distance tothe opening edge 35 in the air outlet 45, FIG. 2, of the vane motor 11.Via the orifice 33 and passages 32 the pressure in the working cylinder13 is thus transmitted to the chamber of valve housing 25 and actsagainst the piston face 27 therein.

From the air outlet 45 the air is directed via a peripheral groove andradial bores 36 to a sound mufiler 37 containing sound damping sinteredrings 38 whereupon the air via openings 39 is let out into the open air.

During tightening of a nut the operator holds the nut setting tool andinserts the square boss 17 into a wrench sleeve, not shown, which hasbeen placed around the nut. The shut-off valve 24 is in the positionshown in FIG. 1. Accordingly the piston face 26 is actuated by thepressure in the air supply connection portion 18 and keeps the shut-offvalve 24 open against the action of the spring 28. The opening positionis defined by an annular abutment 40 in the valve housing 25 againstwhich a radial flange 41 on the shut-off valve 24 bears.

When the trigger 22 is actuated compressed air will flow via the airsupply connection 18 -18 to the vane motor 11 expanding in the workingcylinder 13 while driving the vanes 12 so that the motor 11 and thus thesquare boss 17 are rotated. At the beginning of the tightening therotational resistance is small, the vane motor 11 rotates rapidly andthe pressure around the orifice 33, which is disposed within theexpansion zone of the working air, will be relatively low. Withincreasing resistance to rotation the number of revolutions and the airconsumption successively decrease so that a raise in pressure takesplace in the air inlet 19. A corresponding raise in pressure takes placeat the orifice 33, in the passage 32, in the chamber of valve housing25, and at the piston face 27, and this pressure raise is amplified bythe expansion being counteracted by air leaking past the vanes 12 to anincreased extent with decreasing number of revolutions and by areduction of the pressure loss at the inlet 19. By adjustment of the setscrew 31 the spring tension in the spring 28 is chosen such as to causethe pressure raise at the piston face 27 to close the shut-off valve 24when the desired final torque has been reached. The shut-off valve 24 inthe open position thereof is disposed at a relatively short distancefrom the seat 23. The air flow passing the valve 24 therefore builds upa pressure differential at opposite sides of the valve flange 41. Thispressure differential increases strongly during the shut-off movementand causes the shut-off valve to rapidly snap to closed position whenthe desired shut-off pressure has been built up in the valve housing 25.

Since the air supply connection portions 18 18 downstream of the valveseat 23, upon closing the valve 24, are exhausted via the vane motor 11,the shut-off valve 24 will remain closed by the spring 28 as long as thetrigger 28 is depressed. A bore 42 passes through the seat 23 and allowsthe passage of bleed air in parallel with the closed shut-off valve 24';As soon as the trigger 22 is released and the throttle valve 20 closes,the bore 42 consequently causes pressure equalization in the air supplyconnection portions 18 18 at opposite sides of the valve seat "23,. As aresult herewith the pressure acting on the piston face 26 will open theshut-off valve 24 and the nut setting tool 10 will be ready for a newtightening operation.

In cases when the tightened nut joint is capable of elastic rebound, thekinetic energy of the rotating parts will be absorbed during closing ofthe shut-01f valve by the joint without annoying increase of thereaction force taken up by the operator. In case 'of a rigid joint onecan counteract the appearance of too large a reaction force by areduction of the incoming pressure in the air supply connection portion18 causing a reduction of the number of revolutions. This isaccomplished by angular adjustment of a throttling .valve 43 or athrottling screw inserted in the air supply connection portion 18 inwhich portion the pressure of the incoming air can be reduced to thedesired extent by throttling.

What I claim is:

1. A rotary pneumatic torque release tool comprising a housing, aworking cylinder in said housing, a vane motor rotatably mounted betweeninlet and outlet ports in said cylinder for driving said tool, an airsupply connection for connecting said inlet port to a source ofcornpressed air, a control mechanism in said housing to be released forperforming a control movement affecting the operation of said tool uponthe development of a predetermined torque therein, adjustable pressuresensing means operatively connected to said control mechanism forreleasing said control movement thereof in response to a predeterminedraise in the pressure sensed by said sensing means, and passage means insaid housing separate from said connection, said passage meanscommunicating said sensing means with an orifice in said Workingcylinder subjected to the drive pressure therein acting directly on thevanes for rotating said motor.

2. A torque release tool according to claim 1 in which said orifice isdisposed within a sector of said cylinder bounded by the closing edge ofsaid inlet port and half the angular distance to the opening edge ofsaid outlet port.

3. A rotary pneumatic torque release tool comprising a housing, aworking cylinder in said housing, a vane motor rotatably mounted betweeninlet and outlet ports in said working cylinder for driving said tool,an air supply connection for connecting said inlet port to a source ofcompressed air, a shut-off valve in said connection movable to open andshut positions relative thereto, means for normally maintaining saidvalve in open position, adjustable pressure sensing means operativelyconnected to said valve for causing movement thereof to shut position inresponse to a predetermined raise in the pressure sensed by said sensingmeans, and passage means in said housing separate from said connection,said passage means communicating said sensing means with an orifice insaid working cylinder subjected to the drive pressure therein actingdirectly on the vanes for rotating said motor.

4. A rotary pneumatic torque release tool comprising a housing, aworking cylinder in said housing, a vane motor rotatably mounted betweeninlet and outlet ports in said cylinder for driving said tool, an airsupply connection for connecting said inlet port to a source ofcompressed air, a shut-off valve in said connection movable to open andshut positions relative thereto, a first surface on said valve subjectedto pressure in said connection for normally maintaining said valve inopen position, a chamber adjacent said valve, a second surface on saidvalve connected to said chamber and adapted to move said valve to shutposition in response to a predetermined rise in pressure in saidchamber, and passage means in. said housing separate from saidconnection, said passage means communicating said chamber With anorifice in said cylinder subjected to the drive pressure therein actingdirectly on the vanes for rotating said motor.

5. A torque release tool according to claim 4, in which said shut-oifvalve is biased by spring means to shut position, and means foradjusting the bias of said spring means to adjust the magnitude of thepressure in said chamber causing said valve to shut.

6. A torque release tool according to claim 4 in which said valve is aseat valve with one face thereof exposed to pressure in said connectionand the other to pressure in said chamber.

7. A torque release tool according to claim 4 in which there is provideda manually actuatable throttle valve in said connection downstream ofsaid shut-oif valve and a bleed passage in parallel with said shut-offvalve for pro- References Cited UNITED STATES PATENTS 7/1964 Gattiker91S9 X 3/1968 Whitehouse 91-59 X EVERETTE A. POWELL, JR., PrimaryExaminer US. Cl. X.R.

